Changes in subtidal assemblages in a scenario of warming: Proliferations of ephemeral benthic algae in the Canary Islands (eastern Atlantic Ocean) |
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Affiliation: | 1. CIIMAR/CIMAR,Centro Interdisciplinar de Investigação Marinha e Ambiental, Terminal de Cruzeiros do Porto de Leixões, Av. General Norton de Matos s/n, 4450-208, Matosinhos, Portugal;2. Stazione Zoologica Anton Dohrn, Villa Comunale, 80121 Naples, Italy;3. cE3c-Centre for Ecology, Evolution and Environmental Changes/Azorean Biodiversity Group - Universidade dos Açores, Rua da Mãe de Deus 13A, 9501-801 Ponta Delgada, Azores, Portugal;4. MARE, Marine and Environmental Science Centre, Laboratório de Ciências do Mar, Universidade de Évora, Avenida Vasco da Gama, Apartado 190, 7521-903 Sines, Portugal;5. CMMG-Centro do Clima, Meteorologia e Mudanças Globais da Universidade dos Açores, Pólo Universitário de Angra do Heroísmo, 9701-851 Angra do Heroísmo, Azores, Portugal |
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Abstract: | The present work analysed the main changes in subtidal algal assemblages in the last decade in an oceanic archipelago (Canary Islands – eastern Atlantic Ocean). Changes result from increases in cover of ephemeral benthic algae, such as the non-native chlorophyte Pseudotetraspora marina and the native cyanophytes Blennothrix lyngbyacea, Schizothrix calcicola and Schizothrix mexicana. Ephemeral algae overgrow subtidal assemblages which are extensively dominated by Lobophora variegata, but competitively do not exclude other species. Increases in the abundance of species coincided with a warming of about 2 °C in surface seawater temperature (SST) linked to the weakening of the Cold Canary Current and the Northwestern African upwelling. Shifts in the distribution and cover of ephemeral species follow the SST gradient from warmer waters in the western islands to colder waters in the eastern ones. While in the warmest western islands, species have spread quickly colonizing all type of substrates in just a few years (2005–2008), the occurrence of ephemerals towards the coldest eastern islands is yet inconspicuous. |
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